[dev.typeparams] cmd/compile/internal/types2: report constant overflow in binary ops

[dev.typeparams] cmd/compile/internal/types2: report constant overflow in binary ops

This is the go.types changes of https://golang.org/cl/271706
ported to types2.

Also: Fixed a bug in the go/types version (was using the
wrong position in the error message).

Change-Id: I798b80243a66f0be5b943a6951d7a1ff769abca2
Reviewed-on: https://go-review.googlesource.com/c/go/+/271806
Trust: Robert Griesemer <gri@golang.org>
Reviewed-by: Robert Findley <rfindley@google.com>